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Methicillin-Resistant Staphylococcus aureus Endocarditis from a Diabetic Foot Ulcer
Understanding and Mitigating the Risk
Diabetic foot infections are a common cause of morbidity and mortality in the United States, and successful treatment often requires an aggressive and prolonged approach. Recent work has elucidated the importance of appropriate therapy for a given severity of diabetic foot infection, and highlighted the ongoing risk such patients have for subsequent invasive life-threatening infection should diabetic foot ulcers fail to heal. The authors describe the case of a man with diabetes who had prolonged, delayed healing of a diabetic foot ulcer. The ulcer subsequently became infected by methicillin-resistant Staphylococcus aureus (MRSA). The infection was treated conservatively with oral therapy and minimal debridement. Several months later, he experienced MRSA bloodstream infection and complicating endocarditis. The case highlights the ongoing risk faced by patients when diabetic foot ulcers do not heal promptly, and emphasizes the need for aggressive therapy to promote rapid healing and eradication of MRSA.
Immigration Brings New Pathology with No Standardized Treatment Protocol
Madura Foot Case Studies Phialemonium and Phaeoacremonium
Madura foot is an uncommon invasive soft-tissue infection that foot and ankle specialists encounter. We present two rare cases of Phialemonium and Phaeoacremonium fungi infections of the foot diagnosed in northern California to inform physicians on the presentation and current treatment options for this unique pathology. The two cases presented outline the clinical presentations, diagnostic data, and surgical and antimicrobial interventions. There is a concentration on the antimicrobial options depending on which of the over 20 species is encountered. The pertinent literature and supporting data are reviewed to create an outline for discussion of treatment protocols when faced with these emerging opportunistic infections.
Foot infections are a common and serious problem in persons with diabetes. Diabetic foot infections (DFIs) typically begin in a wound, most often a neuropathic ulceration. While all wounds are colonized with microorganisms, the presence of infection is defined by ≥2 classic findings of inflammation or purulence. Infections are then classified into mild (superficial and limited in size and depth), moderate (deeper or more extensive), or severe (accompanied by systemic signs or metabolic perturbations). This classification system, along with a vascular assessment, helps determine which patients should be hospitalized, which may require special imaging procedures or surgical interventions, and which will require amputation. Most DFIs are polymicrobial, with aerobic gram-positive cocci (GPC), and especially staphylococci, the most common causative organisms. Aerobic gram-negative bacilli are frequently copathogens in infections that are chronic or follow antibiotic treatment, and obligate anaerobes may be copathogens in ischemic or necrotic wounds.
Wounds without evidence of soft tissue or bone infection do not require antibiotic therapy. For infected wounds, obtain a post-debridement specimen (preferably of tissue) for aerobic and anaerobic culture. Empiric antibiotic therapy can be narrowly targeted at GPC in many acutely infected patients, but those at risk for infection with antibiotic-resistant organisms or with chronic, previously treated, or severe infections usually require broader spectrum regimens. Imaging is helpful in most DFIs; plain radiographs may be sufficient, but magnetic resonance imaging is far more sensitive and specific. Osteomyelitis occurs in many diabetic patients with a foot wound and can be difficult to diagnose (optimally defined by bone culture and histology) and treat (often requiring surgical debridement or resection, and/or prolonged antibiotic therapy). Most DFIs require some surgical intervention, ranging from minor (debridement) to major (resection, amputation). Wounds must also be properly dressed and off-loaded of pressure, and patients need regular follow-up. An ischemic foot may require revascularization, and some nonresponding patients may benefit from selected adjunctive measures. Employing multidisciplinary foot teams improves outcomes. Clinicians and healthcare organizations should attempt to monitor, and thereby improve, their outcomes and processes in caring for DFIs.
Background
We aimed to evaluate surrogate markers commonly used in the literature for diabetic foot osteomyelitis remission after initial treatment for diabetic foot infections (DFIs).
Methods
Thirty-five patients with DFIs were prospectively enrolled and followed for 12 months. Osteomyelitis was determined from bone culture and histologic analysis initially and for recurrence. Fisher exact and χ2 tests were used for dichotomous variables and Student t and Mann-Whitney U tests for continuous variables (α = .05).
Results
Twenty-four patients were diagnosed as having osteomyelitis and 11 as having soft-tissue infections. Four patients (16.7%) with osteomyelitis had reinfection based on bone biopsy. The success of osteomyelitis treatment varied based on the surrogate marker used to define remission: osteomyelitis infection (16.7%), failed wound healing (8.3%), reulceration (20.8%), readmission (16.7%), amputation (12.5%). There was no difference in outcomes among patients who were initially diagnosed as having osteomyelitis versus soft-tissue infections. There were no differences in osteomyelitis reinfection (16.7% versus 45.5%; P = .07), wounds that failed to heal (8.3% versus 9.1%; P = .94), reulceration (20.8% versus 27.3%; P = .67), readmission for DFIs at the same site (16.7% versus 36.4%; P = .20), amputation at the same site after discharge (12.5% versus 36.4%; P = .10). Osteomyelitis at the index site based on bone biopsy indicated that failed therapy was 16.7%. Indirect markers demonstrated a failure rate of 8.3% to 20.8%.
Conclusions
Most osteomyelitis markers were similar to markers in soft-tissue infection. Commonly reported surrogate markers were not shown to be specific to identify patients who failed osteomyelitis treatment compared with patients with soft-tissue infections. Given this, these surrogate markers are not reliable for use in practice to identify osteomyelitis treatment failure.
